Vol 32, No 4 (2019)

The influence of sintering of an aerogel sample on spectral line parameters of carbon monoxide confined inside aerogel pores is studied for the first time. The measurements were carried out in the 4000–4400 cm^–1 spectral range using the Bruker IFS 125HR spectrometer. It is shown that the sintering increased CO halfwidths but did not affect rotational dependences of CO lines.

Carbon monoxide (CO) is a marker of the atmospheric pollution caused by fires and combustion engine emissions. The regular monitoring of the CO content in the atmosphere is needed to control air quality. In this work, the results of CO atmospheric total column retrievals from the solar spectra recorded by Fourier -transform spectrometers at the St. Petersburg (59.88° N, 29.83° E) and Kourovka (57.038° N, 59.545° E) stations are presented. The impact of differences in CO absorption line parameters in modern spectroscopic databases on the accuracy of the CO atmospheric total column retrieved from high resolution spectra is estimated.

The impulse response of a diffuse non-line-of-site underwater communication link at a wavelength of 0.5 μm is simulated using a modified double local estimate Monte Carlo algorithm for base distances between the source and receiver from 10 to 100 m. The power of radiation received and the maximal data rate are estimated based on the impulse response.

An algorithm for interpreting light backscattering matrices (LBSMs) obtained experimentally on the unique high-altitude polarization lidar of the National Research Tomsk State University in the process of cirrus cloud sounding is described. In terms of the database of LBSMs calculated theoretically within the framework of the physical optics approximation, microphysical characteristics of cirrus clouds such as the particle size, orientation, and shape, as well as the percentage of particles with different shapes, are estimated.

We study how the atmospheric aerosol influences the recorded emission of the Earth’s upper atmosphere. The study was performed using the data from an automatic CIMEL CE-318 sun photometer, a part of the global network of ground-based sun photometer stations (AERONET), and observations were made of atomic oxygen [OI] 557.7- and 630-nm emission lines at the Geophysical Observatory of the Institute of Solar-Terrestrial Physics, Siberian Branch, Russian Academy of Sciences (52° N, 103° E). A nonlinear characteristic of the correlation dependence was revealed between the intensities of the 557.7- and 630-nm emissions of the upper atmosphere and the aerosol optical depth (AOD): the correlation coefficients increased for small AOD (below 0.5) and decreased for large turbidities. We identified an observation period with a high positive correlation between the 557.7-/630.0-nm emission intensities and the AOD, presumably associated with vast forest fires.

Results of the theoretical study of the propagation of femtosecond pulses of a Ti:Sapphire laser in air under self-focusing and filamentation are presented. The self-focusing of laser pulses is analyzed on the basis of the method of diffraction-beam tubes. The analysis established that specific light structures were formed in a laser beam during self-focusing. One of such structures is an energy-replenishing diffraction-beam tube, which provides the necessary energy for filamentation and has the form of a high-intensity light channel during postfilamentation pulse propagation. The dependences of the radius and power of the energy-replenishing tube on the initial beam radius and peak power at a fixed pulse length are derived. It is revealed that the energy consumption of radiation for the filamentation decreases with an increase in the beam radius. The peak power contained in the energy-replenishing light tube during the postfilamentation laser pulse propagation does not exceed the critical self-focusing power of a Gaussian beam and weakly depends on the initial pulse parameters.

We present the results of complex experimental studies of gas admixtures and the vertical structure of aerosol in the atmosphere over the Lake Baikal in July 2018 onboard research vessel Academician V.А. Koptyug. Simultaneously, the observations were performed at the Boyarsky stationary station, located in the southeastern part of Lake Baikal. We describe briefly the instrumentation used in the experiments and discuss certain preliminary results of analyzing the data obtained.

Results of experimental studies of the acoustic field generated by a supersonic jet on the vertical jet facility of the Institute of Theoretical and Applied Mechanics are presented. The measurements are carried out using nine microphones arranged symmetrically with respect to the jet axis. The shape of the phase front of the acoustic wave, as well as spectra of the broadband acoustic noise and discrete components with a high time and spatial resolution are analyzed. It is shown that the turbulence structure in the acoustic field is inhomogeneous and is formed by several sources.

We present the results of devising new techniques and technical means for utilizing small-sized unmanned aerial vehicles (UAVs) in ecological monitoring of marine water basins in compliance with the MARPOL 73/78 international convention. The development of a hardware-software complex is described for the system of recognizing oil spills using elements of artificial intelligence. The laboratory experiments on identifying oil spills by laser induced fluorescence (LIF) methods are presented, as well as the methods of recording the spectrum of upward solar radiation.

The influence of the brightness amplifier operation mode on images formed with a bistatic laser monitor is studied. The bistatic laser monitor is an active optical system with two active elements. A possibility of imaging remote (to more than 5 m) objects with this instrument is evaluated. It is shown that a change in the concentration of active substance (copper bromide) of the amplifier significantly affects the amplification of the input signal. The active substance temperature rise from 480 to 550°C increases the gain throughout the input signal range. A further increase in the temperature (up to 570°C) increases the gain only at a relatively weak input signal (less than 100 mW). The resulting amplification characteristics of the active optical system are described and compared with the parameters of images formed (distortion and brightness).